refactored mock for test_app_add_team_view.py.

using decorator instead context manager.
refactored mock for test_app_env_view.py.

using decorator instead context manager.
refactored mock for test_app_team_view.py.

using decorator instead context manager.
refactored mock for test_create_app_view.py.

using decorator instead context manager.
refactored mocks for test_list_app_view.py.

using decorator instead context manager.